Free TX PACT: Essential Academic Skills (Subtest II: Writing) (702) Practice Test

Read the passage below; then answer the question that follows. (Part 1) Coral reefs are among the most biologically diverse ecosystems on Earth. (Part 2) They cover less than one percent of the ocean floor, yet they support roughly a quarter of all marine species. (Part 3) Reefs form over thousands of years as tiny animals called polyps deposit calcium carbonate. (Part 4) Many coastal communities depend on reefs for food, tourism revenue, and protection from storm surges. (Part 5) Rising ocean temperatures, however, now threaten these fragile structures. Which part most effectively functions as the thesis statement for this passage?